This invention relates to bubble-pack thermal and moisture resistant insulation materials for use in the construction of buildings, roads, septic fields, aircraft runways and the like.
It is well known to use separating sheets of materials to thermally separate construction materials from underground soils. These materials are also used to hold and retain the different layers of sand and rocks used in the construction of roads which under the repetitive action of freeze and thaw leads to cracks and holes in the exposed external layer of the roads. These materials are also used as moisture barriers in buildings under construction, especially underneath the concrete floor of the basement that otherwise would be directly in contact with the soil and the moisture.
However, the aforesaid materials are generally formed as rigid or semi-rigid insulating panels which have a strong tendency to crack and break apart under heavy loads which, thus decreases their efficacy. Furthermore, they are difficult to install and are limited in size because of transportation problems.
Further, although, these materials are made in such a way that they do not transfer heat by conduction or convection, they generally have a relatively high reflective surface material that still allows radiation heat transfer that is fairly significant for large surfaces.
Insulation materials are also know which comprise a clean, non-toxic, heat barrier made of aluminum foil bonded to a single or double layer of polyethylene-formed bubbles spaced one bubble from another bubble in the so-called xe2x80x9cbubble-packxe2x80x9d arrangement. Non-foil bubble-packs are used extensively as packaging material, whereas the metal foil bubble-pack sheet is used as thermal insulation in wood frame structures, walls, attics, crawl spaces, basements and the like and as wrapping for hot water heaters, hot and cold water pipes, air ducts and the like. The reflective surface of the metal, particularly, aluminum foil enhances the thermal insulation of the air-containing bubble-pack.
Generally, low density polyethylene films of 1-12 mil, optionally, with various amounts of linear low density polyethylene in admixture when additional strength is required, are used for the above applications. The insulating properties of the bubble pack primarily arise from the air in the voids. Typically, bubble diameters of 1.25 cm, 0.60 cm and 0.45 cm are selected.
In certain environments, the aluminum foil of the prior art assemblies are vulnerable to chemical attack or delamination from the thermoplastic film by reason of being exposed to detrimental chemicals, acidic or alkaline vapours or the like.
Further, to reduce the risk of such undesired chemical attack and, also, to utilize the radiative insulative property of the aluminum surface, a space or gap is left between the prior art assembly and the wall, strut and the like adjacent the assembly. This results in a relatively larger combined unit than would otherwise be desired.
There is, therefore a need for a thermal and moisture resistant, insulation pack for use in road and building construction that is of a simple form, low cost to manufacture which is flexible, easy to carry and apply, provides reduced radiative heat transfer and provides reduced total unit construction volume.
It is an object of the present invention to provide an enhanced thermal and moisture resistant insulation sheet for use in road and building construction that is sufficiently flexible as to be readily adapted to be carried, installed and enhanced weight resistant.
It is a further object to provide a thermal and moisture insulation sheet which is environmentally more stable to attack on the metal and delamination.
It is a further object to provide a thermal and moisture resistant insulative sheet for use in abutement with an adjacent wall, strut and the like to provide an insulative barrier system of reduced thickness.
Accordingly, in one aspect, the invention provides a composite bubble-pack assembly comprising (i) a first bubble-pack having a first thermoplastic film having a plurality of portions wherein each of said portions defines a cavity and a second thermoplastic film in sealed engagement with said first film to provide a plurality of closed said cavities; (ii) a second bubble-pack having a third thermoplastic film having a plurality of portions wherein each of said portions defines a cavity and a fourth thermoplastic film in sealed engagement with said third film to provide a plurality of closed said cavities; and (iii) a film selected from the group consisting of a thin foil of metal or a metallized thermoplastic film interposed between and bonded to said first bubble-pack and said second bubble-pack.
The terms xe2x80x9ccavityxe2x80x9d or xe2x80x9ccavitiesxe2x80x9d in this specification include voids, bubbles or other like closed spaces. The cavities may be formed of any desired suitable shape, such as, for example, of a semi-cylindrical, oblong or rectangular form. However, a generally hemi-spherical cavity is preferred.
The number, size and layout of the bubble in the pack according to the invention may be readily selected, determined and manufactured by the skilled artisan. Typically, in a single pack, the bubbles are arrayed in a coplanar off-set arrangement. Each of the hemi-spherical bubbles may be of any suitable diameter and height protruding out of the plane of the bonded films. Typically, the bubble has a diameter selected from 0.5 cm-5 cm, preferably 0.8-1.5 cm; and a height selected from 0.2 cm-1 cm, preferably 0.4 cm-0.6 cm. A preferred bubble-pack has an array of about 400 bubble per 900 cm2.
The thermoplastic films may be formed of any suitable polymer or copolymer. The first, second, third and fourth films may be formed of the same or different material. Most preferably, the assembly has each of the thermoplastic films formed of a polyethylene or a nylon. A most preferred plastic is polyethylene, particularly a low-density polyethylene, optionally, in admixture with a linear low density polyethylene of use as aforesaid first and second films.
The composite assembly of the invention further comprises one or more foils, layers, films, laminates or the like of a suitable metal, for example, aluminum or a metallized thermoplastic film within the assembly to enhance reflection of infra-red radiation.
Preferably, the aluminum foil forms part of the laminate having the foil heat sealed between a pair of polyethylene films to provide a better seal to the pair of bubble arrays.
The composite bubble-pack assembly according to the invention is of particular value when used in an environment that has a detrimental effect on the exposed metal when the latter is used as an outer film on bubble packs according to the prior art. Since, in the present invention, the metal is, in effect, embedded in a double thermoplastic-air-filled void system, it is remote from metal-attaching chemicals or an environment which effects metal-thermoplastic film delamination.
Further, I have found that in order for the metal foil to be efficacious in providing reflective heat reduction when bonded as an outer film, there needs to be a gap or space between the metal foil and adjacent wall, ground or like member. This, thus, often results in a thicker than desired insulative assembly. In contrast, the composite assembly according to the invention has an inherently built-in air space adjacent each side of the metal foil to provide the desired reflective property. This, thus, offers a more compact fully insulative package, sheet and the like than the prior art.
Thus, the assembly according to the invention comprises an insulative sheet that provides air spaces on both sides of a metal or metallized foil which provides thermal and moisture insulation enhancement to the assembly and physical protection to the foil, in the rough and tough environment of placement adjacent to concrete, soil and other natural ground conditions, comprising particulate matter such as gravel and lime.
The sheet according to the invention is flexible and easy to apply to cover objects of a plurality of shapes.
The sheet effects useful reduction of heat transfer in each of the conduction, convection and radiation modes, notwithstanding the relative thinness of the sheet.
Further, the metal foil is protected from direct attack by most chemical agents that do not attack the thermoplastic layers.